1. Field of the Invention
The present invention relates to a sewing machine provided with a projector for projecting the image of a desired stitch pattern on a workpiece to enable the confirmation of the desired stitch pattern and, more particularly, to a sewing machine provided with a projector and a workpiece holding means capable of shifting a workpiece between a stitching area and an image projecting area.
2. Description of the Related Art
Various sewing machines have been proposed which are capable of enabling the confirmation of a stitching starting position and the arrangement of a stitch pattern to be formed on a workpiece prior to starting stitching operation.
The applicant of the present patent application has previously proposed a sewing machine provided with a visual display, i.e., a CRT display, in Japanese Patent Laid-open No. 63-105787. The visual display of this prior sewing machine displays both a maximum stitching area and a stitching area, namely, an area to be covered by a desired stitch pattern, to enable the operator to confirm the stitch pattern.
A control system for controlling the operation of a computerized embroidery machine in the initial stage of operation is disclosed in Japanese Patent Laid-open No. 63-197488. This prior control system moves an embroidery frame without vertically moving the needle to enable the operator to confirm a stitching area on a workpiece held by the embroidery frame.
The sewing machine disclosed in Japanese Patent Laid-open No. 63-105787 displays both a maximum stitching area and a stitching area to be covered by a desired stitch pattern on the CRT display. Accordingly, the operator is able to estimate approximately the position of the stitch pattern on the workpiece relative to the embroidery frame. However, it is impossible to confirm the position of the stitch pattern accurately. For example, in forming a stitch pattern on a patterned workpiece or in additionally forming a stitch pattern on an embroidered workpiece, the accurate estimation of the position of the stitch pattern on the workpiece is difficult.
The control system for controlling the operation of a computerized embroidery machine in the initial stage of operation disclosed in Japanese Patent Laid-open No. 63-197488 enables the operator to decide if a desired pattern can be formed in an area defined by the embroidery frame. However, the control system is unable to enable the operator to confirm the position of the stitch pattern on the workpiece accurately, which is a problem similar to that residing in the sewing machine disclosed in Japanese Patent Laid-open No. 63-105787.
The applicant of the present patent application proposed a sewing machine capable of projecting the image of a stitch pattern in an area on the bed before the stitching point or on a workpiece placed on the bed in U.S. Ser. No. 07/602,699, now U.S. Pat. No. 5,072,680, which is not prior art. In this previously proposed sewing machine, a stitching area and an image projecting area are not demarcated exactly and the image of a stitch pattern is formed in an area before the stitching point to enable the operator to confirm a stitch pattern forming area on the workpiece accurately. However, this image projecting system cannot be applied without modification to an embroidery machine using an embroidery frame, because the stitching point at the start of stitching operation, in most cases, is in the central area of a stitching area on a workpiece defined by the embroidery frame, and hence the shadows of the presser foot, the presser bar, the needle bar and the needle, which are the essential components of the embroidery machine, fall on the projected image of a stitch pattern when the image of the stitch pattern is formed in an area before the stitching point. Therefore, the accurate confirmation of the stitch pattern is impossible and an effective image projecting area is limited to an area only on the feed side with respect to the presser foot and the needle bar. Accordingly, the accurate projection of the image of a stitch pattern is impossible if this known image projecting system is applied directly to the embroidery machine, which forms a stitch pattern in substantially the entire stitching area.